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cRIO NI 9214 / 9213: "Open Thermocouple Detection" problem

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Hello all

 

I am facing a problem with the cRIO 9214 module, in particular the "Open Thermocouple Detection" function. I guess the problem is similar with NI 9213 modules as NI 9213/9214 modules are very similar.

 

Environnement

I am acquiring a thermocouple measurement with a cRIO NI 9214 module plugged in a slave 9144 chassis. This chassis is connected in EtherCAT to a Deskotp Real-time target.

The "Open Thermocouple Detection" function is actived on the NI 9214 module.

The code is developped in Labview 2012 SP1.

 

I am using the Scanned engine (and not FPGA). I am using the "scanned access mode" (and not direct access). Thus the reading is done with a "Scanned variable read" VI. An example source code is provided.

code.jpg

 

 

Test

1) At the beginning of the test, a thermocouple is electrically connected. When I start the test, I can read the measured temperature and no error is returned by the "Scanned variable read" VI. This is ok so far.

 

2) When I electrically disconnect the thermocouple, the read value becomes "0" and the "Scanned variable read" VI returns the error code "–65582", corresponding to the "open thermocouple error". This is still ok.

 

3) However, when I reconnect again the thermocouple, the read value keeps being "0" and the "Scanned variable read" VI keeps returning the error code "–65582".

This is not expected a there is not anymore an open thermocouple.

 

4) When I stop the Scanned Engine and restart it, the temperature is correctly read again with no error returned.

 

 

Question / Issue

Why the "Open Thermocouple Detection" does not detect automatically that a thermocouple is connected again?

How should I do to be able to measure again the temperature, if a thermocoupe is accidentally disconnected and reconnected? I can not stop and restart the scanned engine in my application. Is there any way to "reset" the error and read again the temperature values?

 

This link mentions the following properties: OpenThrmcplChansExist and OpenThrmcplChans. It seems that these properties can reset any error. However I could not find them, at least in Scanned engine mode. Is there something I did not figure out?

 

Any help would be greatly appreciated.

 

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Solution
Accepted by topic author bidouille404

I found a solution : the problem comes from the NI 9144 firmware version. Downgrading from rev_2.6 to rev_2.4 solved the problem.

 

To sum up about this v2.6 firmware bug:

Temperatures are not read correctly when thermocouples are electrically disconnected/reconnected when using NI 9214 modules with NI 9144 chassis, with OTD (Open Thermocouple Detection) active. The read value is "0" and the NI 9144 returns error "–65582" (open thermocouple detected) even when a thermocouple is reconnected.

Using NI 9144 firmware rev2.4 instead of rev2.6 solves the problem.

 

Test environnement:

Real Time Desktop target

NI 9144 slave chassis

NI 9214 module with OTD active and firmware rev2.6

Scanned engine

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How do I determine the firmware version on my 9214?

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It sounds like the problem wasn't with the firmware of the 9214 but rather with the firmware of the EtherCAT chassis.  You can download firmware to the device following the directions in the manual linked below.

 

http://www.ni.com/pdf/manuals/372498g.pdf

 

You can find the different firmware revisions at Program Files\National Instruments\NI-Indcom for EtherCAT and should see something to the effect of "NI 9144 <rev#>.foe".  If I remember correctly, the revisions mostly follow the release numbers with perhaps a few exceptions (I think 14.5 still uses revision 14).

Matt J | National Instruments | CLA
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